textproduct: Rapid City

KEY MESSAGES

- Chances for isolated storms/showers daily.

- Chance for a couple severe storms this afternoon across southwest and south central SD.

- Warming up for the weekend.

UPDATE

Issued at 930 PM MDT Wed Aug 26 2026

Pos theta-e adv can be expected tonight across the western SD Plains. This may support elevated isolated shra/TS there through morning as a weak impulse traverses NW flow aloft. Deep layer moisture will spread into the region Thur per SE ll flow. This will support 1500-2000 J/kg of MLCAPE by afternoon. Weak CIN coupled with a passing impulse will support TS chances by afternoon, esp across scentral SD and SW SD. Deep layer shear of 40 to 50 knots will support the potential for supercells as storms progress SE. Have adjusted pops for this. Otherwise, isold shra/ts will be possible Thur night across the NW, with low chances continuing through much of the weekend.

DISCUSSION

(This Evening Through Wednesday) Issued at 114 PM MDT Wed Aug 26 2026

Current upper air models show ridge over the Rockies, with northwest flow over the forecast area. 19Z surface analysis shows high pressure over western North Dakota this afternoon, while a frontal boundary sits over eastern Wyoming into Nebraska. Winds are currently light and variable over the area, with temperatures in the 80s. Satellite shows some CU development over the Black Hills, otherwise mostly clear skies.

An isolated strong to severe storm cannot be ruled out this afternoon and evening. The best chance for storms will be in the Black Hills, as well as northeast Wyoming to southwest SD closer to the frontal boundary. CAPE values in the 200-500 j/Kg range along with eff shear 30-40kts and modest lapse rates will support a small hail and wind threat if any storms are able to get going. Another weak disturbance progged to move through the region Thursday, bringing more isolated storm chances, mainly over the Black Hills to southwestern SD. Later Thursday into Friday the upper ridge moves over the region, prompting warmer temperatures, with highs over the weekend ranging from the upper 80s to near 100. Sunday into Monday an upper low treks across the northern plains and southern Canada, however better forcing looks to remain north of our area. Cannot rule out some showers and storms on Sunday, mainly over northwestern SD.

As the upper low slides eastward, pattern shifts for our region, with southwest flow setting up early next week. This will lower temperatures a bit before shortwave ridging moves back in Tuesday. In typical August fashion, weak disturbances will bring near daily chances for isolated showers and storms.

AVIATION

(For the 18Z TAFS Through 18Z Friday) Issued At 1103 AM MDT Thu Aug 27 2026

Ongoing destabilization is evident from bubbling cumulus over the Black Hills. Storms are still possible this afternoon, however the most likely region for initiation will be southern Black Hills with a mostly SE storm motion. PROB30 has been kept in for KRAP in case a rogue storm forms further north than anticipated. Stronger storms will be capable of large hail, strong gusty erratic winds, and heavy downpours. Afterwards, VFR conditions are expected along with gusty winds in northeast WY overnight.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.